diff --git a/src/kiri/conf.js b/src/kiri/conf.js
index c6e1c0c6..6499fb5a 100644
--- a/src/kiri/conf.js
+++ b/src/kiri/conf.js
@@ -655,7 +655,8 @@
                 exportPreview: false,
                 decimate: true,
                 detail: "good",
-                animesh: "200"
+                animesh: "200",
+                healMesh: false
             },
             // label state preferences
             labels: {
diff --git a/src/kiri/init.js b/src/kiri/init.js
index f7413b84..b71f8569 100644
--- a/src/kiri/init.js
+++ b/src/kiri/init.js
@@ -152,6 +152,7 @@
         control.exportLocal = UI.exportLocal.checked;
         control.exportPreview = UI.exportPreview.checked;
         control.decimate = UI.decimate.checked;
+        control.healMesh = UI.healMesh.checked;
         SPACE.view.setZoom(control.reverseZoom, control.zoomSpeed);
         // platform.layout();
         API.conf.save();
@@ -1645,6 +1646,7 @@
             parts:            UC.newGroup(LANG.pt_menu, $('prefs-prt'), {inline: true}),
             detail:           UC.newSelect(LANG.pt_qual_s, {title: LANG.pt_qual_l, action: detailSave}, "detail"),
             decimate:         UC.newBoolean(LANG.pt_deci_s, booleanSave, {title: LANG.pt_deci_l}),
+            healMesh:         UC.newBoolean(LANG.pt_heal_s, booleanSave, {title: LANG.pt_heal_l}),
 
             prefadd:          UC.checkpoint($('prefs-add')),
 
@@ -2373,6 +2375,7 @@
             UI.reverseZoom.checked = control.reverseZoom;
             UI.autoSave.checked = control.autoSave;
             UI.decimate.checked = control.decimate;
+            UI.healMesh.checked = control.healMesh;
             lineTypeSave();
             detailSave();
             updateFPS();
diff --git a/src/kiri/slicer.js b/src/kiri/slicer.js
index 515bb1e9..94816a56 100644
--- a/src/kiri/slicer.js
+++ b/src/kiri/slicer.js
@@ -530,6 +530,9 @@
             // for topo slices, we just need the raw lines
             if (!topoMode && !simpleMode) {
                 slice.groups = connectLines(slice.lines, slice.z);
+                if (options.union) {
+                    slice.groups = POLY.flatten(POLY.union(POLY.nest(slice.groups), null, true), null, true);
+                }
                 if ((debug && slice.lines.excessive) || xray) {
                     const dash = xray || 3;
                     slice.lines.forEach((line, i) => {
diff --git a/src/mode/fdm/slice.js b/src/mode/fdm/slice.js
index 9981bcff..74b9540e 100644
--- a/src/mode/fdm/slice.js
+++ b/src/mode/fdm/slice.js
@@ -151,6 +151,7 @@
             height: sliceHeight,
             minHeight: sliceMinHeight,
             firstHeight: firstSliceHeight,
+            union: settings.controller.healMesh,
             // debug: true,
             // xray: 3,
             // view: view
diff --git a/web/kiri/lang/en.js b/web/kiri/lang/en.js
index 5783548e..d545d80d 100644
--- a/web/kiri/lang/en.js
+++ b/web/kiri/lang/en.js
@@ -164,6 +164,8 @@ kiri.lang['en-us'] = {
     pt_deci_l:      "enable or disable point decimation\nduring port import. for faster slicing\nand lower memory usage",
     pt_qual_s:      "quality",
     pt_qual_l:      "level of detail to retain\nduring slicing operations\nlower is faster",
+    pt_heal_s:      "heal mesh",
+    pt_heal_l:      "attempt to heal\nnon-manifild meshes",
 
     xp_menu:        "exports",